1. Field of the Invention
This invention pertains to retort systems for generally flat containers, and more particularly relates to a system for heating or cooling filled, thin walled generally flat containers having fast heat penetration rates for more evenly and efficiently heating all containers in a batch of containers to assure a uniformly cooked product.
2. Description of the Prior Art
Agitating and non-agitating batch type high pressure cookers and coolers are well known in the art. In general these retort systems receive batches of containers, such as cylindrical cans or jars, which are first heated by hot water until sterilized and are thereafter cooled by cold water. In order to prevent damage to the containers where the pressure within the containers exceeds the pressure externally of the containers, an overriding air pressure is usually applied over the water in these prior art devices. Also, if the water within the pressure vessel or retort is circulated, it is usually merely cascaded down upon the flat upper ends of the upper containers, or is moved horizontally against the rounded surfaces of the outer upstream containers, with little regard to whether or not the lower tiers of containers and the containers near the middle of the batch of containers receive the same amount of heat as the upper or outer containers.
The U.S. Pat. No. Davis 2,629,312 issued Feb. 24, 1953, is somewhat pertinent to the present invention in that the patentee discloses a pressure cooker or retort system arranged to receive a plurality of containers in retort baskets on an elongated reel. The baskets are moved into the cooker or retort on wheels formed integrally with each basket. The baskets are also rotated during processing in response to rotating the elongated reel. In the Davis apparatus steam, not hot water, is used as the heating medium.
Prior U.S. Pat. No. 3,480,451 to Hardison, issued Nov. 25, 1969, also discloses a retort having trackways for receiving cases of bottled goods, and drive means for rotating the entire retort during processing.
Prior U.S. Pat. No. 3,744,402 to Piegza et al, issued July 19, 1973, discloses a retort having a plurality of article supporting baskets mounted for rotation with a rotatable fluid distributing shaft assembly. One end wall of the retort, and the baskets, are moved along tracks to expose the baskets for loading and unloading.
Prior U.S. Pat. No. 3,776,257 to Piegza, issued Dec. 4, 1973 discloses a high pressure retort with flat walls which separate an article and liquid filled treatment chamber from the outer curved areas of the retort thereby reducing the amount of liquid processing medium required. A gas pressure is applied to the external surfaces of the flat walls to prevent pressure induced bowing of the flat walls.
An apparently unpatented retort system is also known wherein batches of cylindrical cans standing on end are positioned within a pressure vessel between vertical side walls. The cans are cooked by using a fan to draw hot air from an inlet end between the side walls past the cans and thereafter returning the hot air to the inlet end externally of the side walls. After cooking, the cans are cooled by directing sprays of cold water downwardly onto the cans.
Although broadly pertinent to the present invention it will be apparent that none of the above patents disclose controlled circulation of the processing liquids parallel to the walls of flat containers as in the present invention.